Marine propeller with periodically adjustable blades



June 6, 1967 c. A. LINDAHL 3,323,593

MARINE PROPELLER WITH PERIODICALLY ADJUSTABLE BLADES Filed March l2, 1965 5 Sheets-Sheet l INVENTOR CARL AXEL Ll NDAHL HIS ATTORNEYS June 6, 1967 c. A. LINDAHL 3,323,598

MARINE PROPELLER WITH PERIODICALLY ADJUSTABLE BLADES 5 Sheets-Sheet 2 Filed March 12, 1965 Fig.3

INVIENTOR CARL AXEL LINDAHL HIS ATTORNEYS June 6, 1967 c. A. LINDAHL 3,323,598

MARINE PROPELLER WITH PERIODICALLY ADJUSTABLE BLADES Filed March 12, 1965 5 Sheets-Sheet s Fig. 5

INVENTQR CARL AXEL LINDAHL BY m'fiw MMQMJM,

HIS ATTORNEY June 6, 1967 C. A. LINDAHL MARINE PROPELLER WITH PERIODICALLY ADJUSTABLE BLADES Filed March 12, 1965 5 Sheets-Sheet 4 24d ew INVENTOR CARL AXEL LINDAHL BY M. @WM

H 18 AT TORN 5Y5 June 6, 1967 c. A. LINDAHL 3,323,598

MARINE PROPELLER WITH PERIODICALLY ADJUSTABLE BLADES Filed March 12, 1965 5 Sheets-Sheet 5 Fig.7

INVENTOR CARL AXEL. LIN DAHL.

BY M; EMQMWM HIS ATTORNEYS United States Patent 3,323,598 MARINE FROPELLER WITH PERIODICALLY ADJUSTABLE BLADES Carl A. Lindahl, Kristinehamn, Sweden, assignor to Aktieholaget Karlstads Mekaniska Werlkstad, Karlstad, Sweden, a company of Sweden Filed Mar. 12, 1965, Ser. No. 439,327 5 Claims. (Cl. 170160.25)

This invention relates to improvements in variable pitch marine propellers, and more particularly to an improved variable pitch propeller in which the pitches of the blades of the propeller can be varied individually and periodically.

A marine propeller usually operates in a field of liquid flow where velocity varies in magnitude and direction. Thus the propeller blade sections operate under varying angles of attack during each revolution of the propeller. The varying angle of attack is undesirable with regard to cavitation and propeller efiiciency and may also cause serious shaft and hull vibrations. By adjusting the pitch of the propeller blades to compensate for the varying flow during each revolution of the propeller, the undesirable effects mentioned above can be reduced. This may be achieved by periodically varying the pitch angle of each propeller blade with respect to a mean pitch value during the propeller rotation. The instantaneous pitch angle will thus depend on the angular position of the propeller blade around the axis of rotation of the propeller when the blades are successively set to the same pitch angle at the same angular position.

In order to vary the pitch angle of one propeller blade, it would appear that when the propeller is rotating and the ship moving, so great a power input will be needed to change the pitches of the propeller blades that it will be practically impossible to use a programmed blade movement of the above-mentioned type, if a separate source of power for individual variation of the pitch angle of the blades is to be used.

In accordance with the present invention, a variable pitch propeller including means for periodically or cyclically varying the pitches of the blades of the prepeller is provided, and in which little or no additional power is required for periodically varying the pitches of the individual blades.

The present invention is based on the discovery that, if the pitch angle of a propeller blade is varied periodically, in relation to the angular blade position around the axis of rotation of the propeller, a power input for adjustment of the blade pitch angle is needed during certain parts of the propeller revolution only, while during the remainder of each revolution of the propeller the blade will supply power to the device for adjustment of the blade pitch angle. With a propeller having two or more blades, the blades are in different angular positions around the axis of rotation of the propeller and are thus in different parts of the periodical adjustment of the pitch angle of the blades. Due to this fact, at least during certain intervals some of the blades will require power for pitch angle adjustment, while the remaining blades supply power when the pitch angle is adjusted. The result is that the power output of a five-bladed propeller having some of the propeller blades supplying power for setting the blade pitch angle, will be higher than the input necessary for setting of the pitch angle of the remaining blades during the entire time of one propeller revolution. With fewer propeller blades, for example three or four, a coordination is obtained which, at least during great parts of one propeller revolution, considerably reduces the total power input needed at any moment to set the pitch angles of all blades.

A characteristic feature of the invention is that the 3,323,598 Patented June 6, 1967 power or reaction delivered by one propeller blade as its pit-ch is changed during part of the propeller revolution is transferred to those blades which require an input of additional power for variation of their pitch angles.

A device by which this operation is carried out may, according to the invention, suitably include a non- -rotating, closed cam arranged around the axis of rotation of the propeller. The cam is to be shaped and so located in relation to the axis of rotation of the propeller, that its position varies in axial or radial direction in accordance with the guiding function desired. Besides, the device includes a number of elements or bodies corresponding to the number of propeller blades. These elements are placed around the axis of rotation of the propeller in cor.- respondence to the blades and rotate together with the propeller, while at the same time they are running in power-transferring contact with the cam, at least in that direction, in which the position of the cam varies in relation to the axis of rotation of the propeller. Each of these cam followers is connected through power-transferring means to the pivot of its propeller blade in such a way that each blade is turned around its longitudinal axis, i.e., its pitch angle varies in accordance with the movement of the cam follower. Through the non-rotating cam, an exchange of power is effected between the different propeller blades so that no power needs to be supplied for the periodical variation of the pitch angle of the blades, if the number of propeller blades is high enough for a complete coordination. Even in case the number of propeller blades is too small to accomplish a complete coordination, the exchange of output over the cam will cause a reduction of the total input needed and such input will be taken from the propeller shaft. Thus, no extra source of power will be necessary for the periodical operation of the propeller blade pitch angle.

Following is a detailed description in connection with the accompanying drawings, which comprise diagrams showing the way of operating according to the invention and, as an example, a device embodying the invention.

FIGURE 1 is a diagram of the torque needed in order to vary the pitch angle of one propeller blade sinusoidally around a mean value in relation to the angular position of the blade around the axis of rotation of the propeller during one propeller revolution;

FIGURE 2 is a diagram showing the input of power which must be supplied to the propeller blade and the output of power the same blade delivers on such a variation of the blade pitch angle, respectively;

FIGURE 3 is a diagram showing the variation of the input needed for each propeller blade of a five-bladed propeller as a function of the angular position of the propeller during one revolution;

FIGURE 4 is a diagram on the total input needed for variation of the pitch angles of all the blades;

FIGURE 5 is a longitudinal sectional view of a propeller with a device to govern the variation of the pitch angle of the propeller blades according to the invention, including an eccentric radial bearing;

FIGURE 6 is a view in radial section through the governing mechanism for variation of the pitch angle of the propeller blades, taken partly on line AA, partly on line BB and partly on line C-C in FIGURE 5; and

FIGURES 7 and 8 are views in section taken on lines EE and FF of FIGURE 6.

On the diagram, FIGURE 1, the curve G represents the variation of the pitch angle of one propeller blade round an average value as a function of the angular position of the blade round the axis of rotation of the propeller during one propeller revolution. The blade pitch angle varies sinusoidally, with a period corresponding to one propeller revolution. The curve H represents the angular speed for the propeller blade rotation round its longitudinal axis, i.e., the speed with which the blade pitch angle changes, as a function of the angular blade position round the axis of rotation of the propeller during one propeller revolution. The curve I finally shows the torque the propeller blade develops round its longitudinal axis when its pitch angle is varied in accordance with the curves G and H. This torque is caused by the effect of the water on the propeller blade when the propeller is rotating and the ship is moving as well as by the propeller blade movement and friction in the hub mechanism. The curves represent at constant propeller rpm. and constant ship speed with a five-bladed propeller, but are in its general form valid also for a propeller with another number of blades and are also essentially independent of the mean value, round which the propeller blade pitch angle varies. As shown by the curves, FIG- URE 1, the torque which the propeller blade exerts round its longitudinal axis during certain parts of the propeller revolution is exerted in the direction to assist the blade pitch angle, while it, during other parts of the propeller revolution, opposes the change of the pitch angle. Of this, it is concluded that during certain portions of the propeller revolution power has to be supplied to change the blade pitch angle in the way desired, while during other portions of the propeller revolution the blade itself assists in changing its pitch angle and thus supplies an output to those devices which govern the pitch angle variations. Since the output and input respectively stand in proportion to the product of torque and the angular speed with which the propeller pitch angle varies, the curve K, see FIGURE 2, shows the input momentarily required for changing the blade pitch angle, as a function of the blade angular position of the blade around the axis of rotation of the propeller during one propeller revolution. Positive values of curve K (FIGURE 2) indicate that the propeller blade delivers an output to the devices which turn the propeller blade around its longitudinal axis. On the other hand, negative values mean that an input has to be supplied to the propeller blade from these turning devices.

On the diagram, FIGURE 3, the individual power requirements for all the five propeller blades have been shown as functions of the angular position of the propeller during one propeller revolution, while the curve, FIGURE 4, constitutes the sum of power requirements for adjustment of the pitch angles for all the propeller blades during one revolution. As will be understood, the curve of FIGURE 4 has a positive value during the entire propeller revolution, i.e., the propeller blades, collectively, supply always a certain output to the devices which vary the pitch angles of the propeller blades. Such output is via the propeller blades taken from the running speed of the ship and is, in a governing mechanism according to the invention, at least partly consumed by the losses owing to friction, while an eventually remaining output is transmitted to the propeller shaft.

FIGURE 5 shows a device embodying the invention, for periodically varying the pitches of the propeller blades according to a sinusoidal function in relation to the angular position of the propeller blades around the axis of rotation of the propeller during a period corresponding to one revolution of the propeller, in which connection both the amplitude and the mean value for the periodical variation are adjustable.

FIGURE 5 shows a propeller shaft 1, at the outer end of which the properller bub 2 is fixed. Around the propeller hub 2 the propeller blades 3 are pivoted in the hub so that they can be turned around their longitudinal axes and thus brought into different pitch angle positions. Each propeller blade is carried in the propeller hub by a shaft or blade dowel 4, which by different known means, not shown in the drawings, is connected to a piston rod 26d forming a part of the mechanism for periodically varying the pitch angle of each propeller blade 3. A suitable connection between the piston rod 26d and a corresponding propeller blade is shown in U.S. Patent No. 3,013,615 dated Dec. 19, 1961. The mechanism shown also in FIGURE 6 includes a circular cam or ring 11 encircling the propeller shaft 1 perpendicular thereto. The ring 11 is adjustable into any desired eccentric relation to the propeller shaft 1. The eccentricity of the ring 11 can be adjusted by means of two pairs of hydraulic cylinders 12 and 13, respectively, which are placed perpendicular to each other, between the ring 11 and two rings 14 pivoted around the propeller shaft. The ring 11 is kept in the adjusted eccentric position in relation to the propeller shaft 1 by these hydraulic cylinders and is prevented from rotating by a dowel or shaft 15 which is slidably mounted in a spherical bearing 17 in the holder 16. The rings 14 are restrained against rotation by means of two arms 18 extending radially and fixed to the rings. The outer ends of the arms 18 extend into spherical bearings 19 in standards 20 fixed to the ring 11. The ring 11 serves as radial hearing or cam with adjustable eccentricity and is provided with an internal groove 21 extending around the inside of the ring. A number of blocks 22 corresponding to the number of propeller blades slide in the groove 21. Each sliding block 22 is connected to the piston 240 in a hydraulic cylinder 24 having two chambers 24a and 24b mounted on the propeller shaft 1. It will be understood that each propeller blade has a corresponding cylinder 24 and the following associated system, only one of which is described hereinafter. A pipe 25 in the propeller shaft 1 connects the chamber 24a to the chamber 26a in the hydraulic cylinder 26 located in the propeller hub 2. The other chamber 24b of the cylinder 24 is connected to the chamber 26b in the cylinder 26 in the propeller hub 2, by means of a pipe 27 in the propeller shaft 1. The propeller hub 2 contains thus a number of cylinders 26 corresponding to the number of propeller blades 3, only one being shown in FIGURE 5. The piston 260 in each one of the cylinders 26 is connected by means of a piston rod 26d to a crank (not shown) on the pivot 4 for the corresponding propeller blade 3, so that the position of the piston 26c corresponds to the pitch angle of the propeller blade 3 and the propeller blade pitch angle in consequence can be varied by moving this piston 260. Each pair of cylinders 24 and 26 forms thus a closed hydraulic transmission system completely filled with pressure fluid. In this system the piston 26c is forced to move in accordance with the movement of the piston 24c in the cylinder 24 located in the governing mechanism.

As the propeller rotates, the sliding blocks 22 will slide in the groove 21 in the eccentric ring 11, and the radial distance of each sliding block 22 to the axis of rotation of the propeller will vary according to a sine function with a period corresponding to one propeller revolution. The pistons 240 in the cylinders 24 will be reciprocated and will cause a corresponding reciprocating movement of the pistons 260 in the propeller hub 2. Accordingly, the pitch angles of the propeller blades 3 are periodically varied in accordance with the radial movement of the sliding blocks 22. The magnitude of the periodical variation of the propeller blade pitch angle is determined by the extent of eccentricity of the ring 11 relative to the propeller shaft 1, while the phase position of the periodical variation of the pitch angle is determined by the direction in which the center of the ring 11 is moved, in offset relation to the axis of rotation of the propeller. Those propeller blades 3, which at a certain moment tend to change in pitch in the same direction as the governing mechanism tends to turn them, will press the sliding blocks 22 against the ring 11 with forces which tend to move the sliding blocks 22 in the direction of rotation of the propeller shaft 1, and they will thus supply to the propeller shaft 1 a corresponding input. At the same time, those propeller blades 3 which tend to change pitch in a direction opposite to the one the control mechanism determines, will cause the sliding blocks to react against the ring 11 with forces which tend to oppose the rotation of the propeller shaft 1 and thus consume a corresponding amount of power from the propeller shaft 1. A continuous exchange of power is thus effected between the propeller blades, so that no or only an insignificant amount of power need be supplied for the periodically varying stitch anae of the nroaeller blades 3.

In order for the piston 260 in each of the cylinders 26 located in the propeller hub 2 to follow up exactly the movement of the piston 240 in the corresponding cylinder 24 in the governing mechanism, the volume of pressure fluid in the cylinders and in the pipings connecting the cylinders must be constant. As a constant volume is diflicut to obtain because of leakage, a control system is required to assure that the piston 260 in a cylinder 26 continuously takes the correct position, and causes the corresponding propeller blade 3 to assume the pitch angle which is determined by the position of the piston 246 in the cylinder 24. In the embodiment of the invention shown, such a control system includes a control valve 29 (FIGURES 6 and 8) for each propeller blade 3 and for each pair of cylinders 24 and 26. This control valve 29 consists of a slide valve plug 31 which is axially movable in a valve sleeve 30 slidable in a casing 29a in the shaft housing. Valve sleeve 30 and valve plug 31 are formed so that the plug lands 31a and 3111 cover or close the ports 30a and 30b connected to opposite chambers 24a and 26a and 24b and 26b in the cylinders 24 and 26. As the valve plug 31 is moved from a central position in one direction in relation to the valve sleeve 30, pressure fluid from a fluid pressure source admitted at the port 30a is transmitted to the chambers 24:: and 26a in the two cylinders 24 and 26, while corresponding quantity of pressure fluid is discharged from the other chambers 24b and 26b of the cylinders through the return port 30d or Site to the low pressure side of the source. The piston 260 in the cylinder 26 is moved and so the pitch angle of the propeller blade 3 is changed, but position of the piston 24c in the corresponding cylinder 24 is not changed because of its connection tothe ring 11. If, however, the valve slide 31 is moved from zero position in the other direction in relation to the valve sleeve 30, the control valve 29 transmits pressure fluid to the two chambers 24b and 26b in the cylinders 24 and .26 and discharges a corresponding amount of pressure fluid from the chambers 24a and 26a so that the piston 266 in the cylinder 26 is moved in opposite direction and changes the pitch angle of the propeller blade 3 connected to it in the other direction, the piston 240 in the cylinder 24 located in the governing mechanism remaining in unchanged relation to the ring 11.

The outer end of the slide valve plug '31 is connected to a two-armed lever arm 32 (FIGURES 6 and 8) which at one end 33 is coupled to the piston rod 24a in the cylinder 24. The other end 34 of the lever 32 is connected to a rod 35, radially movable relative to the propeller shaft 1, which rod 35 is biased radially outwardly by the spring 36. The inner end of the rod 35 is connected to a cable 37. or the like (FIGURES 5 and 7), which extends along the propeller shaft 1 and around pulleys 37a 37b and is connected to the pivot 4 of the propeller blade 3 so that the rotary motion of the propeller blade 3 around its longitudinal axis is converted to a corresponding radial movement of the rod 35. The lever 32 is connected to the rod 35 and to the piston 24c in the cylinder 24 so that, as the piston 24c is moved in one direction and hereby causes a corresponding change of the pitch angle of the propeller blade 3, the piston 24c and the rod 35 will tend to move the two arms of the lever 32 equally great angles, and the turning-point of the lever 32 will remain stationary so that the valve slide 31 is not moved and the control valve 29 is ineffective. If, however, the pitch angle of the propeller blade 3, caused by movement of the piston 240 in the clylinder 24, is incorrect on account of leakage or other disturbance in the hydraulic system, the two ends 33 and 34 of the lever 32 will not move equally and the pivot point of the lever 32 will be moved. Such movement also causes the valve plug 31 to be moved from its center position in relation to the valve sleeve 3t) and the control valve 29 admits and discharges a suflicient amount of pressure fluid to the two cylinders 24 and 26 to return the valve plug 31 to its central position, which occurs when the pitch angle of the propeller blade 3 has been adjusted to the correct value determined by the position of the piston 240 in the cylinder 24.

It is obvious that the mean value, relative to which the pitch angles of the propeller blades are periodically varied by the governing mechanism, will be determined by the central position for the valve plug 31 in the control valves 29. The control vales 29 have, therefore, been designed so that their neutral position can be adjusted to set a desired mean pitch angle for all of the propeller blades 3. The central position of the control valves 29 can be adjusted by moving the valve sleeves 30 relative to the plug 31. The movement and the adjustment of the valve sleeves 30 of all the control valves 29 is accomplished simultaneously by connecting each valve sleeve 3d at its inner end to an arm of a bell-crank lever 38 (FIGURES 5 and 8), having another arm engaged slid ably in a groove 39 on a control rod 40. By moving the control rod 40 it is thus possible to move all of the valve sleeves 30 in all the control valves 29 for all the propeller blades 3 radially with respect to the arms of the shaft 1 so that the control valves get a new central position and the propeller blades 3 thus get a new mean pitch angle around which the pitch angle of each propeller blade is varied periodically with an amplitude determined by the eccentricity of ring 11.

The above-described device embodying the invention should be considered as an example of the invention. Other devices or modifications are possible within the scope of the invention. It is thus possible with a governing mechanism of the type shown on FIGURES 5 to 8 to have the propeller blades 3 connected to the sliding blocks 22 by means of mechanical link mechanisms instead of hydraulic connections. Even non-sinusoidal variations of the pitch angle of the propeller blades in relation to the angular position of the blades can, of course, be achieved without departing from the invention.

1 claim:

1. A variable pitch marine propeller comprising a propeller hub, a plurality of blades mounted for rotation thereon for variation of the pitches thereof, a nonrotatable cam, means for adjusting said cam eccentrically relative to the axis of said propeller hub, a cam follower corresponding to each of said blades engaging said cam and movable rotatably with said propeller and relative to said hub in engagement with said cam, power-transmitting means connecting each cam follower with its corresponding blade for supplying power for increasing the pitch of each blade in response to rotation of said propeller, and supplying power to rotate said propeller in response to decrease in pitch of each blade by reaction against rotation of said propeller and blade, said powertransmitting means comprises for each blade a first hydraulic cylinder having a first piston reciprocable therein and dividing said cylinder into first and second chambers, means connecting said piston to a cam follower for movement therewith, a second hydraulic cylinder having a second piston reciprocable therein and dividing said second cylinder into first and second chambers, means connecting said second piston to a propeller blade for rotating said blade to change its pitch, piping connecting said first chambers of said first and second cylinders, and piping connecting said second chambers of said first and second cylinders, said chambers and said piping being adapted to be filled with liquid, whereby movement of said first piston by said cam produces a corresponding pitch change of said propeller blade.

2. The propeller set forth in claim 1 in which said power-transmitting means comprises valves for intro ducing liquid selectively into one of said first and second chambers of said second cylinders and discharging liquid simultaneously from the other of said first and second chambers of said second cylinders, and means for actuating said valves simultaneously and equally to move said pistons equal distances in said second cylinders.

3. The propeller set forth in claim 1 in which said power-transmitting means comprises means responsive to non-corresponding movement of said first piston and pitch change of said blade for selectively admitting liquid into and discharging liquid from said chambers of said first and second cylinders to make said pitch change correspond to movement of said first piston.

4. The propeller set forth in claim 1 in Which said power-transmitting means comprises valves for intro ducing liquid selectively into one of said first and second chambers of said second cylinders and discharging liquid simultaneously from the other of said first and second chambers of said second cylinders, means for actuating said valves simultaneously and equally to move said pistons equal distances in said second cylinders, and means including said valves responsive to non-corresponding movement of said first piston and the pitch change of a blade for selectively admitting liquid into and discharging liquid from said chambers of said first and second cylinders to render said pitch change and said movement of said first piston corresponding.

5. The propeller set forth in claim 1 in which said power-transmitting means comprises valves for introducing liquid selectively into one of said first and second chambers of said second cylinders and discharging liquid simultaneously from the other of said first and second chambers of said second cylinders, means for actuating said valves simultaneously and equally to move said pistons equal distances in said second cylinders, and means including said valves and linkage connecting said blade and said first piston and responsive to non-corresponding movement of said first piston and the pitch change of a blade for selectively admitting liquid into and discharging liquid from said chambers of said first and second cylinders to render said pitch change and said movement of said first piston corresponding.

References Cited UNITED STATES PATENTS 769,621 9/1904- Manker 170160.25 1,370,587 3/1921 Jackson 170-46025 FOREIGN PATENTS 325,538 2/1930 Great Britain.

126,385 6/1959 Russia.

MARTIN P. SCHWADRON, Primary Examiner.

EVERETTE A. POWELL, IR., Examiner. 

1. A VARIABLE PITCH MARINE PROPELLER COMPRISING A PROPELLER HUB, A PLURALITY OF BLADES MOUNTED FOR ROTATION THEREON FOR VARIATION OF THE PITCHES THEREOF, A NONROTATABLE CAM, MEANS FOR ADJUSTING SAID CAM ECCENTRICALLY RELATIVE TO THE AXIS OF SAID PROPELLER HUB, A CAM FOLLOW CORRESPONDING TO EACH OF SAID BLADES ENGAGING SAID CAM AND MOVABLE ROTATABLY WITH SAID PROPELLER AND RELATIVE TO SAID HUB IN ENGAGEMENT WITH SAID CAM, POWER-TRANSMITTING MEANS CONNECTING EACH CAM FOLLOWER WITH ITS CORRESPONDING BLADE FOR SUPPLYING POWER FOR INCREASING THE PITCH OF EACH BLADE IN RESPONSE TO ROTATION OF SAID PROPELLER, AND SUPPLYING POWER TO ROTATE SAID PROPELLER IN RESPONSE TO DECREASE IN PITCH OF EACH BLADE BY REACTION AGAINST ROTATION OF SAID PROPELLER AND BLADE, SAID POWERTRANSMITTING MEANS COMPRISES FOR EACH BLADE A FIRST HYDRAULIC CYLINDER HAVING A FIRST PISTON RECIPROCABLE THEREIN AND DIVIDING SAID CYLINDER INTO FIRST AND SECOND CHAMBERS, MEANS CONNECTING SAID PISTON TO A CAM FOLLOWER FOR MOVEMENT THEREWITH, A SECOND HYDRAULIC CYLINDER HAVING A SECOND PISTON RECIPROCABLE THEREIN AND DIVIDING SAID SECOND 